Optimizing deep-space optical communication under power constraints

Abstract

We investigate theoretically the efficiency of deep-space optical communication in the presence of background noise. With decreasing average signal power spectral density, a scaling gap opens up between optimized simpledecoded pulse position modulation and generalized on-off keying with direct detection. The scaling of the latter follows the quantum mechanical capacity of an optical channel with additive Gaussian noise. Efficient communication is found to require a highly imbalanced distribution of instantaneous signal power. This condition can be alleviated through the use of structured receivers which exploit optical interference over multiple time bins to concentrate the signal power before the detection stage.

Approaching capacity limits in photon-starved noisy optical communication

“…As a result, in the simplest decoding scenario, the quantum bound on the capacity not only cannot be saturated, but also the transmission rate becomes proportional to the square of the average received signal power, which makes it very small in the photon-starved regime. 8,9 One can improve this result by employing a more general decision rule based on soft decoding and attain a linear scaling of rate with the average received power, however, a potentially large gap still remains to be overcome to approach the quantum bound. 9,10 In this work we show that the quantum bound on communication capacity in the low-power regime in the presence of noise can indeed be attained by employing PPM together with photon-number resolving detectors.…”

“…8,9 One can improve this result by employing a more general decision rule based on soft decoding and attain a linear scaling of rate with the average received power, however, a potentially large gap still remains to be overcome to approach the quantum bound. 9,10 In this work we show that the quantum bound on communication capacity in the low-power regime in the presence of noise can indeed be attained by employing PPM together with photon-number resolving detectors. To approach the capacity bound, it is necessary to utilize a soft decoding strategy and appropriately large PPM orders or, equivalently, the power of the signal light pulse.…”